The present invention relates to a fiber-wired sheet usable for functional optical fiber coils such as optical fiber delay elements and erbium-doped fibers and the like, and a method for manufacturing such a fiber-wired sheet.
Long optical fibers are sometimes used as functional optical fibers such as optical fiber delay elements and erbium-doped fibers. For assembly of an apparatus including a long optical fiber, the optical fiber must be lumped together to be housed in the apparatus. A small bobbin may be used to lump the long optical fiber together. However, using a small bobbin not only makes the entire voluminous but also tends to generate microbending at intersections between the optical fibers and, as a result, may possibly increase the loss.
EPO Publication No. EP1050765A1 discloses an optical fiber holding structure as follows. An optical fiber is arranged in a wound shape with turns displaced from one another in the plane to avoid intersection between portions of the optical fiber. A plurality of turns of the optical fiber are placed in layers at the same position in the thickness direction vertical to the plane in which the optical fiber is arranged. The optical fiber in this state is integrally retained as a sheet with a fixing material such as an adhesive and a film.
The optical fiber holding structure described above being a sheet-like shape as a whole is thin, can be handled integrally without a trouble of coming loose, and can be easily placed in an apparatus. In addition, since the optical fiber is arranged in a wound shape so that no intersection occurs between portions of the optical fiber, the optical fiber can be retained stably without causing microbending and the like.
However, the conventional optical fiber holding structure described above has disadvantages in the aspect of manufacturing efficiency. The optical fiber holding structure is manufactured in the following manner using a manufacturing tool. In the manufacturing tool, two cylindrical winding members for winding an optical fiber are positioned apart from each other by a predetermined distance. A pair of ellipsoidal alignment side plate members are positioned to vertically sandwich the two cylindrical winding members therebetween. One of the alignment side plate members and the two cylindrical winding members are formed integrally. The other alignment side plate member is attached to the cylindrical winding members with bolts or the like. The optical fiber is wound sequentially over the two cylindrical winding members. Upon completion of the winding, the space between the alignment side plate members is filled with a fixing material. The fixing material is hardened to seal the optical fiber with the fixing material as a sheet. The bolts of the manufacturing tool are loosened to detach the alignment side plate member from the optical fiber, and then the optical fiber made integral with the fixing material is released from the manufacturing tool.
As described above, the disclosed optical fiber holding structure requires a complicate manufacturing process. Improvement in manufacturing efficiency is therefore requested.